Heat removal tube set, method for increasing reaction load, and method for producing unsaturated nitrile

Abstract

A heat removal tube set, a method for increasing reaction load by using the heat removal tube set, and application of the same in the production of unsaturated nitrile are provided. The heat removal tube set has at least 10 heat removal tubes, and in at least one and at most 88% of the total of the heat removal tubes of the heat removal tube set, an angle formed between an extended line of the central axis of at least one connecting fitting and an extended line of the central axis of other connecting fitting is greater than 0° and less than 180°. By arranging such a heat removal tube set, the heat removal capability and fluidization efficiency of the fluidized bed reactor is improved, so that the demand for increasing the reaction load can be fully satisfied.

1 . A heat removal tube set (particularly a heat removal water tube set), characterized in that it is configured to be arranged in a heat removal section of a fluidized bed reactor, said heat removal tube set comprising at least 10 (preferably 10 to 100, more preferably 20 to 80) heat removal tubes, said heat removal tube comprising N (N is equal to or greater than 3, preferably N is 3 to 30, more preferably N is 3 to 20) straight pipes and N−1 connecting fittings for connecting any two adjacent straight pipes in series and providing a fluid communication therebetween,
 where the length of the heat removal section along the central axis of the fluidized bed reactor is set as H (in m), a cross section of the heat removal section (referred to as Cross Section A) is obtained by transecting along a direction perpendicular to the central axis of the fluidized bed reactor at a position within the entire region of the length H of the heat removal section (preferably, within the region from 49% H above to 49% H below the central point of the reaction heat removal section, more preferably, within the region from 45% H above to 38% H below the central point of the reaction heat removal section, more preferably, within the region from 40% H above to 8% H below the central point of the reaction heat removal section), 
 for at least one (preferably 1, 2 or 3, or at least 20%, at least 50% or at least 65% of the total) of the heat removal tubes (referred to as profiled heat removal tubes) of the heat removal tube set and at most up to 88% (preferably 75% or 70%) of the total of the heat removal tubes of the heat removal tube set, an angle formed between the extended line of the central axis of the projection on the Cross Section A of at least one (preferably at least 2, 3 or 4, and at most 80%, 90% or 100% of the total) of the connecting fittings of the profiled heat removal tube (preferably excluding the first connecting fitting of the profiled heat removal tube) and the extended line of the central axis of the projection on the Cross Section A of at least one other connecting fitting (preferably the other connecting fitting on the profiled heat removal tube at a position immediately upstream of and in fluid communication with said connecting fitting) is greater than 0° and less than 180° (preferably 30°-150°, more preferably 60°-120°, and further preferably about 90°). 
 
     
     
         2 . The heat removal tube set according to  claim 1 , where the area of the Cross Section A is set as S1 (in m 2 ), and where the sum of the outer contour circumferences of the cross sections of all of the straight pipes of the heat removal tube set on the Cross Section A is set as L1 (in m), L1/S1 is 1.0 to 6.0 m −1  (preferably 2.4 to 5.6 m −1 , more preferably 2.9 to 5.3 m −1 ), and/or the area S1 is 20 to 700 m 2  (preferably 35 to 350 m 2 ), and/or the L1 is 20 to 4200 m, preferably 87.5 to 1225 m. 
     
     
         3 . The heat removal tube set according to  claim 1 , where the total number of the straight pipes in the heat removal tube set in the Cross Section A is set as Nt, the number of straight pipes per unit area of the Cross Section A, i.e. Nt/S1, is 4-16/m 2  (preferably 5-14/m 2 , and more preferably 7-13/m 2 ), and/or the profile of the Cross Section A is circular, elliptical or oval, and preferably circular or substantially circular, and/or the inner profile and the outer contour of the cross section of the straight pipe are circular, elliptical or oval, and preferably circular or substantially circular. 
     
     
         4 . The heat removal tube set according to  claim 1 , characterized in that the heat removal tube set is capable of recovering 1-10 MPa saturated steam (preferably 2-8 MPa saturated steam, more preferably 3-5 MPa saturated steam), and/or has a heat removal capacity of 0.5-3.0 t saturated steam per unit cross-sectional area (m 2 ) per hour, preferably 1.0-2.8 t saturated steam per unit cross-sectional area (m 2 ) per hour, more preferably 1.2-2.4 t saturated steam per unit cross-sectional area (m 2 ) per hour, when evaluated as recovering 4.5 MPa saturated steam, wherein said unit cross-sectional area refers to the unit area of the Cross Section A. 
     
     
         5 . The heat removal tube set according to  claim 1 , wherein for heat removal tube(s) of said heat removal tube set other than said profiled heat removal tube, an angle formed between an extended line of the central axis of the projection of any connecting fitting on said Cross Sectional A and an extended line of the central axis of the projection of another connecting fitting on said heat removal tube at a position immediately upstream or downstream of and in fluid communication with said connecting fitting on said Cross Sectional A is 180°, and/or wherein said heat removal tube comprises a cooling water inlet, and the cooling water inlets of a plurality (preferably 2-8, 2-6 or 2-4) of said heat removal tubes are merged into a cooling water inlet header in said heat removal section, and/or wherein said heat removal tube comprises a cooling water outlet, and the cooling water outlets of a plurality (preferably 2-8, 2-6 or 2-4) of said heat removal tubes are merged into a cooling water outlet header in the heat removal section. 
     
     
         6 . The heat removal tube set according to  claim 1 , characterized in that the outer diameters of the straight pipes are respectively 80-180 mm, preferably 90-170 mm, and/or the inner diameters of the straight pipes are respectively 60-150 mm, preferably 70-140 mm, and/or the lengths of the straight pipes are respectively 4-13 m, preferably 5-12.0 m, and/or the spacing between two adjacent straight pipes on each heat removal tube is 100-700 mm, preferably 150-300 mm, and/or the length H of the heat removal section is 4-13 m (preferably 5-12 m). 
     
     
         7 . The heat removal tube set according to  claim 1 , characterized in that,
 (1) where the full propylene treatment capacity per hour of the fluidized bed reactor is 140-290 kg propylene/m 2  of the Cross Section A, excluding the endpoint of 290, L1/S1 is 1.0-2.5 m −1  (excluding the endpoint of 2.5), preferably 1.4-2.2 m −1 , or   (2) where the full propylene treatment capacity per hour of the fluidized bed reactor is 200-370 kg propylene/m 2  of the Cross Section A, L1/S1 is 1.8-4.6 m −1 , preferably 2.0-4.1 m −1 , or   (3) where the full propylene treatment capacity per hour of the fluidized bed reactor is 290-445 kg propylene/m 2  of the Cross Section A, L1/S1 is 2.5-6.0 m −1 , preferably 2.9-5.3 m −1 .   
     
     
         8 . A fluidized bed reactor, characterized in that it comprises a head, a dilute phase zone, a heat removal section, a pre-reaction section and a cone from top to bottom in sequence, wherein a heat removal tube set according to  claim 1  is arranged in the heat removal section. 
     
     
         9 . A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor according to  claim 8  to obtain an unsaturated nitrile (such as acrylonitrile). 
     
     
         10 . A method for increasing the load of a fluidized bed reactor, wherein the full propylene treatment capacity per hour of the fluidized bed reactor is 140-290 kg propylene/m 2  of the Cross Section A (excluding the endpoint of 290) and L1/S1 is 1.0-2.5 ml (excluding the endpoint of 2.5), the method comprising increasing L1/S1 to 2.5-6.0 m −1 , preferably to 2.9-5.3 m −1 , while increasing the full propylene treatment capacity per hour of the fluidized bed reactor to 290-445 kg propylene/m 2  of the Cross Section A. 
     
     
         11 . A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor to obtain an unsaturated nitrile (such as acrylonitrile), wherein the load of the fluidized bed reactor is increased according to the method for increasing the load as described in  claim 10 . 
     
     
         12 . The method according to  claim 9 , wherein the molar ratio of propylene/ammonia/air (calculated as molecular oxygen) is 1:1.1-1.3:1.8-2.0, the reaction temperature is 420-440° C., the reaction pressure (gauge pressure) is 0.03-0.14 MPa, and the weight hourly space velocity of the catalyst is 0.06-0.15 h −1 .